Spin-orbit torque type magnetoresistance effect element, and method for producing spin-orbit torque type magnetoresistance effect element

ABSTRACT

A spin-orbit torque type magnetoresistance effect element including a magnetoresistance effect element having a first ferromagnetic metal layer with a fixed magnetization direction, a second ferromagnetic metal layer with a varying magnetization direction, and a non-magnetic layer sandwiched between the first ferromagnetic metal layer and the second ferromagnetic metal layer; and spin-orbit torque wiring that extends in a first direction intersecting with a stacking direction of the magnetoresistance effect element and that is joined to the second ferromagnetic metal layer; wherein the magnetization of the second ferromagnetic metal layer is oriented in the stacking direction of the magnetoresistance effect element; and the second ferromagnetic metal layer has shape anisotropy, such that a length along the first direction is greater than a length along a second direction orthogonal to the first direction and to the stacking direction.

This is a Division of application Ser. No. 15/702,290 filed Sep. 12,2017, which claims priority to Japanese Patent Application No.2016-210530, filed Oct. 27, 2016, and Japanese Patent Application No.2017-138384, filed Jul. 14, 2017. The disclosure of the priorapplications is hereby incorporated by reference herein in its entirety.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a spin-orbit torque typemagnetoresistance effect element, and a method for producing aspin-orbit torque type magnetoresistance effect element.

Description of Related Art

Examples of known magnetoresistance effect elements include giantmagnetoresistance (GMR) elements composed of a multilayer film offerromagnetic layers and non-magnetic layers, and tunnelmagnetoresistance (TMR) elements which use insulating layers (tunnelbarrier layers, barrier layers) for the non-magnetic layers. Generally,TMR elements have a larger element resistance than GMR elements, but themagnetoresistance (MR) ratio is larger than GMR elements. Consequently,TMR elements are attracting much attention as elements for magneticsensors, high-frequency components, magnetic heads and non-volatilerandom access memory (MRAM).

MRAM reads and writes data by utilizing the characteristic that when therelative orientation between the magnetizations of two ferromagneticlayers that sandwich an insulating layer is changed, the elementresistance of the TMR element changes. Examples of known methods forwriting to MRAM include a method in which a magnetic field generated byan electric current is used to perform writing (magnetization reversal),and a method in which a spin transfer torque (STT) generated by passingan electric current through the stacking direction of amagnetoresistance effect element is used to perform writing(magnetization reversal).

In recent years, there has been a demand for higher integration of MRAM(for example, see Patent Document 1). In order to achieve high-densityof integration of MRAM, the TMR elements must be made more compact.However, if the TMR elements are made more compact, the magnetizationstability decreases. Decreases in the magnetization stability can causerewriting of data under the influence of heat or the like (for example,see Patent Document 2). MRAM has the purpose of allowing long-termstorage of data, and it is not permissible for the data to bespontaneously overwritten.

As methods for raising the magnetization stability, a method ofincreasing the volume of the ferromagnetic layers and a method ofincreasing the magnetic anisotropic energy of the ferromagnetic layersmay be contemplated. However, magnetic anisotropic energy ismaterial-specific, and depends on the material used in the ferromagneticlayers and the state of the interface between the ferromagnetic layersand the other layers. In order to achieve long-term storage of data, thevolume of the ferromagnetic layers must be made a predetermined size orgreater. For this reason, it is difficult to increase the magneticanisotropic energy without taking these restrictions into consideration.The ferromagnetic layers are thin-films, for which the volumes areapproximately the same as the areas.

RELATED LITERATURE Patent Documents

-   Patent Document 1-   JP 2014-207469 A-   Patent Document 2-   JP 2011-138604 A

Non-Patent Documents

-   Non-Patent Document 1-   I. M. Miron, K. Garello, G Gaudin, P.-J. Zermatten, M. V.    Costache, S. Auffret, S. Bandiera, B. Rodmacq, A. Schuhl, and P.    Gambardella, Nature, 476, 189 (2011).

BRIEF SUMMARY OF THE INVENTION

The intensity of spin transfer torque (STT) is determined by the currentdensity of the electric current flowing in the stacking direction of amagnetoresistance effect element. For this reason, in order to reversethe magnetization by means of spin transfer torque, the current densitymust be a predetermined value or greater. Conversely, in order to raisethe thermal stability of the magnetoresistance effect element, an “areaof a predetermined size or greater” is needed. Thus, in order to drivean element that reverses magnetization by STT, it is necessary tosupply, in the stacking direction of the magnetoresistance effectelement, an electric current having a current amount obtained bymultiplying a “current density of a predetermined value or greater” withan “area of a predetermined size or greater”.

However, if the current amount flowing through a single TMR element orGMR element is too large, the operating life of the element can beaffected. For example, the insulating layers of the TMR element mayundergo insulation breakdown and the element may become incapable ofrecording data.

Additionally, if the current amount flowing through a single TMR elementor GMR element becomes large, then the current amount necessary for theMRAM overall will also become large. For example, when the elements areconnected in parallel, a total current which is the “current amountnecessary for a single element”×the “number of elements” will benecessary in the MRAM overall.

The present invention was made in view of the above-mentioned problems,and has the purpose of providing a spin-orbit torque typemagnetoresistance effect element that has excellent magnetic recordingproperties and that only requires a small amount of current formagnetization reversal.

Accordingly, in recent years, much attention has been focused onmagnetization reversal that utilizes pure spin current generated byspin-orbit interaction or the Rashba effect at the interface betweendifferent materials (for example, see Patent Document 1). Pure spincurrent generated by spin-orbit interaction induces spin-orbit torque(SOT), with this SOT causing magnetization reversal. Further, pure spincurrent generated by the Rashba effect at the interface betweendifferent materials can also cause magnetization reversal by SOT in asimilar manner. A pure spin current is generated when an electron withupward spin and an electron with downward spin flow with the samefrequency in opposing directions, so that the electric charge flowscancel each other out. As a result, the electric current flowing in themagnetoresistance effect element is zero.

The present inventors discovered that if such magnetoresistance effectelements that make use of SOT are used, electric current is not appliedin the stacking direction of the magnetoresistance effect elements, andthe amount of current that is necessary to drive the elements does notdepend on the size of the magnetoresistance effect elements. The presentinventors further discovered a configuration that allows the amount ofcurrent necessary for magnetization reversal of magnetoresistance effectelements to be reduced by making use of SOT.

In other words, the present invention provides the following means forsolving the above-mentioned problems.

(1) The spin-orbit torque type magnetoresistance effect elementaccording to a first embodiment comprises a magnetoresistance effectelement having a first ferromagnetic metal layer with a fixedmagnetization direction, a second ferromagnetic metal layer with avarying magnetization direction, and a non-magnetic layer sandwichedbetween the first ferromagnetic metal layer and the second ferromagneticmetal layer, and spin-orbit torque wiring that extends in a firstdirection intersecting with a stacking direction of themagnetoresistance effect element and that is joined to the secondferromagnetic metal layer; wherein the magnetization of the secondferromagnetic metal layer is oriented in the stacking direction of themagnetoresistance effect element; and the second ferromagnetic metallayer has shape anisotropy, such that a length along the first directionis greater than a length along a second direction orthogonal to thefirst direction and to the stacking direction.(2) In the spin-orbit torque type magnetoresistance effect elementaccording to the above-mentioned embodiment, the magnetoresistanceeffect element may have an elliptical region that is inscribed in aplanar shape of the magnetoresistance effect element when viewed fromthe stacking direction, and an external region that is positionedoutside the elliptical region in the first direction.(3) In the spin-orbit torque type magnetoresistance effect elementaccording to the above-mentioned embodiment, the magnetoresistanceeffect element may be rectangular when viewed from the stackingdirection.(4) In the spin-orbit torque type magnetoresistance effect elementaccording to the above-mentioned embodiment, the length of themagnetoresistance effect element in the first direction may be not morethan 60 nm.(5) In the spin-orbit torque type magnetoresistance effect elementaccording to the above-mentioned embodiment, when end portions of thespin-orbit torque wiring in the second direction are defined as a firstend portion and a second end portion; and of the end portions of themagnetoresistance effect element in the second direction, the endportion on the side closer to the first end portion is defined as athird end portion and the end portion on the side closer to the secondend portion is defined as a fourth end portion; a distance between thefirst end portion and the third end portion and a distance between thesecond end portion and the fourth end portion may both be greater thanzero, and at least one of the distances may be not more than a spindiffusion length of the spin-orbit torque wiring.(6) In the spin-orbit torque type magnetoresistance effect elementaccording to the above-mentioned embodiment, the distance between thefirst end portion and the third end portion may be different from thedistance between the second end portion and the fourth end portion.(7) A method for producing a spin-orbit torque type magnetoresistanceeffect element according to a second embodiment is a method forproducing a spin-orbit torque type magnetoresistance effect elementaccording to the above-mentioned embodiment, the method comprising astep of forming a stacked body having the first ferromagnetic metallayer, and the non-magnetic layer and the second ferromagnetic metallayer, a step of processing the stacked body in one direction; and astep of processing the stacked body, after having been processed in theone direction, in another direction intersecting with the one direction.(8) A method for producing a spin-orbit torque type magnetoresistanceeffect element according to a third embodiment is a method for producinga spin-orbit torque type magnetoresistance effect element according tothe above-mentioned embodiment, the method comprising a step of forminga stacked body having the first ferromagnetic metal layer, and thenon-magnetic layer and the second ferromagnetic metal layer; a step offorming, on one surface of the stacked body, a mask having a rectangularregion in which an ellipse can be inscribed when viewed from thestacking direction of the stacked body, and a projecting region that ispositioned at a corner or a long side of the rectangular region and thatprojects from the rectangular region; and a step of processing thestacked body through the mask.

Based on the spin-orbit torque type magnetoresistance effect elementsaccording to the above-mentioned embodiments, it is possible to raisethe long-term stability of magnetic recording and to reduce the amountof current necessary for magnetization reversal.

Based on the method for producing a spin-orbit torque typemagnetoresistance effect element according to the above-mentionedembodiments, it is possible to easily obtain spin-orbit torque typemagnetoresistance effect elements that have excellent magnetic recordingproperties and that only require a small amount of current formagnetization reversal.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view schematically illustrating a spin-orbittorque type magnetoresistance effect element according to a firstembodiment.

FIG. 2 is a schematic view for explaining the spin Hall effect.

FIG. 3 is a schematic view of a spin-transfer torque typemagnetoresistance effect element using STT.

FIG. 4 is a schematic view of a spin-orbit torque type magnetoresistanceeffect element when the magnetoresistance effect element does not haveshape anisotropy.

FIG. 5 is a diagram illustrating the spin-orbit torque typemagnetoresistance effect element according to the present embodiment,when viewed from the z-direction.

FIG. 6 is a diagram illustrating the spin-orbit torque typemagnetoresistance effect element according to the present embodiment,when viewed from the x-direction.

FIG. 7 is a diagram illustrating the correspondence between the shape ofa photomask and the planar shape of the resulting magnetoresistanceeffect element when viewed from the z-direction.

FIG. 8 is a schematic view for explaining the procedure for producing arectangular magnetoresistance effect element.

FIG. 9 is a diagram schematically illustrating an integrated circuit inwhich a plurality of the spin-orbit torque type magnetoresistance effectelements according to the present embodiment are integrated.

FIG. 10 is a diagram schematically illustrating an integrated circuit inwhich a plurality of the spin-orbit torque type magnetoresistance effectelements according to the present embodiment are integrated.

FIG. 11 is a schematic perspective view illustrating a main portion of acontrol element used in a spin-orbit torque type magnetoresistanceeffect element according to the present embodiment.

FIG. 12 is a diagram for explaining the cell size necessary forarranging one spin-orbit torque type magnetoresistance effect elementand two control elements.

FIG. 13 is a schematic perspective view illustrating the elementstructure of a unit cell when one spin-orbit torque typemagnetoresistance effect element and two control elements are arrangedin accordance with the arrangement in FIG. 12 .

FIG. 14 is a diagram illustrating an arrangement for raising the levelof integration of a spin-orbit torque type magnetoresistance effectelement according to the present embodiment.

FIG. 15 is a diagram for explaining the cell size necessary forarranging one spin-orbit torque type magnetoresistance effect elementand two control elements.

FIG. 16 is a schematic perspective view illustrating the elementstructure of a unit cell when one spin-orbit torque typemagnetoresistance effect element and two control elements are arrangedin accordance with the arrangement in FIG. 15 .

DETAILED DESCRIPTION OF THE INVENTION

The present invention is described below in further detail, withreference to the drawings. The drawings used in the followingdescription may be drawn with specific portions enlarged as appropriateto facilitate comprehension of the features of the present invention,and the dimensional ratios and the like between the constituent elementsmay differ from the actual values. Further, the materials and dimensionsand the like presented in the following examples are merely examples,which in no way limit the present invention, and may be altered asappropriate within the scope of the present invention.

(Spin-Orbit Torque Type Magnetoresistance Effect Element)

FIG. 1 is a perspective view schematically illustrating a spin-orbittorque type magnetoresistance effect element according to a firstembodiment.

The spin-orbit torque type magnetoresistance effect element 100according to the first embodiment has a magnetoresistance effect element10 and spin-orbit torque wiring 20.

In the following description, the stacking direction of themagnetoresistance effect element 10 is deemed the z-direction, a firstdirection along which the spin-orbit torque wiring 20 extends is deemedthe x-direction, a second direction which is orthogonal to both thex-direction and the z-direction is deemed the y-direction.

<Magnetoresistance Effect Element>

The magnetoresistance effect element 10 has a first ferromagnetic metallayer 1 having a fixed magnetization direction, a second ferromagneticmetal layer 2 having a variable magnetization direction, and anon-magnetic layer 3 sandwiched between the first ferromagnetic metallayer 1 and the second ferromagnetic metal layer 2.

The magnetoresistance effect element 10 functions by having theorientation of the magnetization M1 of the first ferromagnetic metallayer 1 fixed in a single direction, whereas the orientation of themagnetization M2 of the second ferromagnetic metal layer 2 is able tovary relatively. When applied to coercive force difference (pseudo spinvalve) MRAM, the coercive force of the first ferromagnetic metal layeris larger than the coercive force of the second ferromagnetic metallayer, and when applied to exchange bias (spin valve) MRAM, themagnetization direction of the first ferromagnetic metal layer is fixedby exchange coupling with an antiferromagnetic layer.

When the non-magnetic layer 3 is formed from an insulator, themagnetoresistance effect element 10 is a tunneling magnetoresistance(TMR) element, whereas when the non-magnetic layer 3 is formed from ametal, the magnetoresistance effect element 10 is a giantmagnetoresistance (GMR) element.

The stacking structure of the magnetoresistance effect element canemploy a conventional magnetoresistance effect element stackingstructure. For example, each layer may be composed of a plurality oflayers, and the structure may also include other layers such as anantiferromagnetic layer for fixing the magnetization direction of thefirst ferromagnetic metal layer 1. The first ferromagnetic metal layer 1is also called the fixed layer or reference layer, whereas the secondferromagnetic metal layer 2 is also called the free layer or the memorylayer.

Conventional materials can be used as the material for the firstferromagnetic metal layer 1. For example, metals selected from the groupconsisting of Cr, Mn, Co, Fe and Ni, and alloys containing at least oneof these metals and having ferromagnetism can be used. Further, alloyscontaining at least one of these metals and at least one element amongB, C and N can also be used. Specific examples include Co—Fe andCo—Fe—B.

Further, in order to achieve higher output, a Heusler alloy such asCo₂FeSi is preferably used. Heusler alloys contain intermetalliccompounds having a chemical composition of X₂YZ, wherein X is a noblemetal element or a transition metal element belonging to the Co, Fe, Nior Cu group of the periodic table, whereas Y is a transition metalbelonging to the Mn, V, Cr or Ti group of the periodic table, and canselect the elemental species of X, and Z is a typical element of groupIII to group V. Specific examples include Co₂FeSi, Co₂MnSi, andCo₂Mn_(1-a)Fe_(a)Al_(b)Si_(1-b).

Furthermore, in order to increase the coercive force of the firstferromagnetic metal layer 1 on the second ferromagnetic metal layer 2,an antiferromagnetic material such as IrMn or PtMn may be used as thematerial that contacts the first ferromagnetic metal layer 1. Moreover,in order to ensure that the leakage magnetic field of the firstferromagnetic metal layer 1 does not affect the second ferromagneticmetal layer 2, a structure having synthetic ferromagnetic coupling maybe used.

Furthermore, in those cases where the orientation of the magnetizationof the first ferromagnetic metal layer 1 is perpendicular to thestacking surface, a stacked film of Co and Pt is preferably used.Specifically, the structure of the first ferromagnetic metal layer 1 maybe [FeB (1.0 nm)/Ta (0.2 nm)/[Pt (0.16 nm)/Co (0.16 nm)]₄/Ru (0.9 nm)/Co(0.24 nm)/Pt (0.16 nm)]₆ in order from the non-magnetic layer 3.

For the material of the second ferromagnetic metal layer 2, aferromagnetic material, and particularly a soft magnetic material, canbe used. Examples of materials that can be used include metals selectedfrom the group consisting of Cr, Mn, Co, Fe and Ni, alloys containing atleast one of these metals, and alloys containing at least one of thesemetals and at least one element among B, C and N. Specific examplesinclude Co—Fe, Co—Fe—B and Ni—Fe.

The orientation of the magnetization of the second ferromagnetic metallayer 2 is z-direction (perpendicular to the stacking surface). In thosecases where the orientation of the magnetization of the secondferromagnetic metal layer 2 is z-direction, the size of themagnetoresistance effect element 10 becomes small. The orientation ofthe magnetization of the second ferromagnetic metal layer 2 isinfluenced by the crystal structure constituting the secondferromagnetic metal layer 2 and the thickness of the secondferromagnetic metal layer 2. The thickness of the second ferromagneticmetal layer 2 is preferably not more than 2.5 nm. Because theperpendicular magnetic anisotropy effect is attenuated as the thicknessof the second ferromagnetic metal layer 2 is increased, the thickness ofthe second ferromagnetic metal layer 2 is preferably kept thin.

Conventional materials can be used as the non-magnetic layer 3.

For example, when the non-magnetic layer 3 is formed from an insulator(and forms a tunnel barrier layer), examples of materials that can beused include Al₂O₃, SiO₂, MgO and MgAl₂O₄. In addition to thesematerials, materials in which a portion of the Al, Si or Mg has beensubstituted with Zn or Be or the like can also be used. Among the abovematerials, MgO and MgAl₂O₄ are materials that enable the realization ofcoherent tunneling, and therefore enable efficient injection of spin.

Further, when the non-magnetic layer 3 is formed from a metal, examplesof materials that can be used include Cu, Au, and Ag and the like.

Furthermore, the magnetoresistance effect element 10 may also have otherlayers. For example, the magnetoresistance effect element 10 may have abase layer on the opposite surface of the second ferromagnetic metallayer 2 from the non-magnetic layer 3, and/or may have a capping layeron the opposite surface of the first ferromagnetic metal layer 1 fromthe non-magnetic layer 3.

A layer disposed between the spin-orbit torque wiring 20 and themagnetoresistance effect element 10 preferably does not dissipate thespin propagated from the spin-orbit torque wiring 20. For example,silver, copper, magnesium, and aluminum and the like have a long spindiffusion length of at least 100 nm, and are known to be resistant tospin dissipation.

The thickness of this layer is preferably not more than the spindiffusion length of the material used for forming the layer. Providedthe thickness of the layer is not more than the spin diffusion length,the spin propagated from the spin-orbit torque wiring 20 can betransmitted satisfactorily to the magnetoresistance effect element 10.

<Spin-Orbit Torque Wiring>

The spin-orbit torque wiring 20 extends along the x-direction. Thespin-orbit torque wiring 20 is connected to one surface of the secondferromagnetic metal layer 2 in the z-direction. The spin-orbit torquewiring 20 may be connected directly to the second ferromagnetic metallayer 2, or connected via another layer.

The spin-orbit torque wiring 20 is formed from a material that generatesa pure spin current by the spin Hall effect when a current flows throughthe material. This material may have any composition capable ofgenerating a pure spin current in the spin-orbit torque wiring 20.Accordingly, the material is not limited to materials formed from simpleelements, and may also be composed of a portion formed from a materialthat generates a pure spin current and a portion formed from a materialthat does not generate a pure spin current.

The spin Hall effect is a phenomenon wherein when an electric current ispassed through a material, a pure spin current is induced in a directionorthogonal to the orientation of the electric current as a result ofspin-orbit interactions.

FIG. 2 is a schematic diagram for explaining the spin Hall effect. FIG.2 is a cross-sectional view of the spin orbit torque wiring 20 shown inFIG. 1 cut along the x-direction. A mechanism by which a pure spincurrent is generated by the spin Hall effect is described with referenceto FIG. 2 .

As illustrated in FIG. 2 , when an electric current I flows along thedirection which the spin-orbit torque wiring 20 extends, a first spin S1oriented toward the back of the paper surface and a second spin S2oriented toward the front of the paper surface are bent in directionsorthogonal to the current. The normal Hall effect and the spin Halleffect have in common the fact that the direction of travel (movement)of the traveling (moving) electric charge (electrons) is bent, butdiffer significantly in terms of the fact that in the common Halleffect, charged particles moving through a magnetic field are affectedby Lorentz forces, resulting in bending of the travel direction, whereasin the spin Hall effect, despite no magnetic field existing, the traveldirection of the spin bends simply under the effect of the movement ofthe electrons (flow of current).

In a non-magnetic material (a material that is not ferromagnetic), theelectron count of the first spin S1 and the electron count of the secondspin S2 are equal, and therefore in FIG. 2 , the electron count of thefirst spin S1 moved to the upward direction and the electron count ofthe second spin S2 moved to the downward direction are equal.Accordingly, the electric current represented by the net flux of theelectric charge is zero. This type of spin current that is accompaniedby no electric current is called a pure spin current.

When a current is passed through a ferromagnetic material, the fact thatthe first spin S1 and the second spin S2 are bent in opposite directionsis the same. However, the difference in a ferromagnetic material is thatone of either the first spin S1 or the second spin S2 is greater,resulting in the occurrence of a net flux for the electric charge (andthe generation of a voltage). Accordingly, a material formed solely froma ferromagnetic substance cannot be used as the material for thespin-orbit torque wiring 20.

If the electron flow of the first spin S1 is represented by J_(↑), theelectron flow of the second spin S2 is represented by J_(↓), and thespin current is represented by J_(S), then the spin current is definedas J_(S)=J_(↑)−J_(↓). In FIG. 2 , the pure spin current J_(S) flows inthe upward direction in the figure. Here, J_(S) is an electron flowhaving 100% polarizability.

In FIG. 1 , when a ferromagnetic material is brought into contact withthe upper surface of the spin-orbit torque wiring 20, the pure spincurrent diffuses and flows into the ferromagnetic material. In otherwords, spin is injected into the magnetoresistance effect element 10.

The spin-orbit torque wiring 20 may contain a non-magnetic heavy metal.Here, the term “heavy metal” is used to mean a metal having a specificgravity at least as large as that of yttrium. The spin-orbit torquewiring 20 may also be formed solely from a non-magnetic metal.

In such a case, the non-magnetic metal is preferably a non-magneticmetal with a large atomic number, and specifically a non-magnetic metalwith an atomic number of 39 or greater having d-electrons or f-electronsin the outermost shell. The reason for this preference is that suchnon-magnetic metals exhibit large spin-orbit interactions that generatea spin Hall effect. The spin-orbit torque wiring 20 may also be formedsolely from a non-magnetic metal with a large atomic number, having anatomic number of 39 or greater and having d-electrons or f-electrons inthe outermost shell.

Typically, when a current is passed through a metal, all of theelectrons move in the opposite direction of the current regardless ofspin orientation, but in the case of a non-magnetic metal with a largeatomic number having d-electrons or f-electrons in the outermost shell,because the spin-orbit interactions are large, the spin Hall effectgreatly acts and the direction of electron movement is dependent on theelectron spin orientation, meaning a pure spin current J_(S) developsmore readily.

Furthermore, the spin-orbit torque wiring 20 may contain a magneticmetal. The term “magnetic metal” means a ferromagnetic metal or anantiferromagnetic metal. By including a trace amount of a magnetic metalin the non-magnetic metal, the spin-orbit interactions can be amplified,thereby increasing the spin current generation efficiency of theelectric current passed through the spin-orbit torque wiring 20. Thespin-orbit torque wiring 20 may also be formed solely from anantiferromagnetic metal.

Spin-orbit interactions occur within interior field peculiar to thesubstance of the spin-orbit torque wiring material. Accordingly, purespin currents also develop in non-magnetic materials. By adding a traceamount of a magnetic metal to the spin-orbit torque wiring material,because the electron spin of the magnetic metal itself is scattered, theefficiency of spin current generation is enhanced. However, if theamount added of the magnetic metal is too large, then the generated purespin current tends to be scattered by the added magnetic metal,resulting in a stronger action reducing the spin current. Accordingly,it is preferable that the molar ratio of the added magnetic metal isconsiderably lower than that of the main component of the pure spincurrent generation portion in the spin-orbit torque wiring. As a guide,the molar ratio of the added magnetic metal is preferably not more than3%.

Furthermore, the spin-orbit torque wiring 20 may contain a topologicalinsulator. The spin-orbit torque wiring 20 may also be formed solelyfrom a topological insulator. A topological insulator is a substance inwhich the interior of the substance is an insulator or a high-resistancebody, but the surface of the substance forms a metal-like state withspin polarization. This substances have a type of internal magneticfield known as a spin-orbit interaction. Accordingly, even if anexternal magnetic field does not exist, the effect of these spin-orbitinteractions generates a new topological phase. This is a topologicalinsulator, which as a result of strong spin-orbit interactions and thebreak of inversion symmetry at the edges, is able to generate a purespin current with good efficiency.

Examples of preferred topological insulators include SnTe,Bi_(1.5)Sb_(0.5)Te_(1.7)Se_(1.3), TlBiSe₂, Bi₂Te₃, and(Bi_(1-x)Sb_(x))₂Te₃. These topological insulators can generate spincurrent with good efficiency.

The spin-orbit torque type magnetoresistance effect element 100 may alsohave other structural elements besides the magnetoresistance effectelement 10 and the spin-orbit torque wiring 20. For example, thespin-orbit torque type magnetoresistance effect element 100 may have asubstrate or the like as a support. The substrate preferably hassuperior smoothness, and examples of materials that can be used includeSi and AlTiC.

(Principles of Spin-Orbit Torque Type Magnetoresistance Effect Element)

Next, the operating principles of the spin-orbit torque typemagnetoresistance effect element 100 will be explained, together withthe specific structure of the magnetoresistance effect element 10 andthe relationship between the magnetoresistance effect element 10 and thespin-orbit torque wiring 20.

As illustrated in FIG. 1 , when a current I₁ is applied to thespin-orbit torque wiring 20, a pure spin current Js (see FIG. 2 ) isgenerated in the z-direction. A magnetoresistance effect element 10 isprovided in the z-direction of the spin-orbit torque wiring 20. Duethereto, spin is injected from the spin-orbit torque wiring 20 into thesecond ferromagnetic metal layer 2 of the magnetoresistance effectelement 10. The injected spin applies a spin-orbit torque (SOT) to themagnetization of the second ferromagnetic metal layer 2, causingmagnetization reversal.

The magnetization reversal of the magnetoresistance effect element 10depends on the amount of injected spin. The amount of spin is determinedby the current density I_(c1) of the electric current I₁ flowing throughthe spin-orbit torque wiring 20. The current density I₁ of the electriccurrent I₁ flowing through the spin-orbit torque wiring 20 is the valueof the electric current flowing through the spin-orbit torque wiring 20divided by the area of a plane orthogonal to the direction of flow ofthe electric current. For this reason, in FIG. 1 , the current densityI_(c1)=I₁/WH. In this case, W represents the length (width) of thespin-orbit torque wiring 20 in the y-direction, and H represents thethickness of the spin-orbit torque wiring 20 in the z-direction.

The current density I_(c1) does not include a component along the lengthL1 of the magnetoresistance effect element in the x-direction, and isdetermined by the spin-orbit torque wiring 20. This is a highlynoteworthy fact. In the spin-orbit torque type magnetoresistance effectelement 100, the amount of current necessary for operation can be setindependently of the area (the area when viewed from the z-direction) ofthe magnetoresistance effect element 10.

FIG. 3 is a schematic view of a spin-transfer torque typemagnetoresistance effect element 101 using STT. The spin-transfer torquetype magnetoresistance effect element 101 comprises a magnetoresistanceeffect element 11, first wiring 30 and second wiring 40. Any kind ofconductor may be used for the first wiring 30 and the second wiring 40.

When a potential difference is provided between the first wiring 30 andthe second wiring 40, an electric current I₂ flows in the stackingdirection of the magnetoresistance effect element 11. The electriccurrent I₂ generates STT, and the magnetization of the secondferromagnetic metal layer 2 is reversed.

The intensity of the STT is determined by the current density I_(c2) ofthe electric current I₂ flowing in the stacking direction of themagnetoresistance effect element 11. The current density I_(c2) of theelectric current I₂ flowing in the stacking direction of themagnetoresistance effect element 11 is the value of the electric currentI₂ flowing in the stacking direction of the magnetoresistance effectelement 11 divided by the area of a plane orthogonal to the direction offlow of the electric current (the cross-sectional area S of themagnetoresistance effect element 11). For this reason, in FIG. 3 , thecurrent density I_(c2)=I₂/S.

This current density I_(c2) has the cross-sectional area S of themagnetoresistance effect element 11 as a parameter. For this reason, theamount of current necessary for the operation of the spin-transfertorque type magnetoresistance effect element 101 depends on the area(the area when viewed from the z-direction) of the magnetoresistanceeffect element 11.

If the cross-sectional area S of the magnetoresistance effect element 11is small, then there is an increased probability that the magnetizationof the second ferromagnetic metal layer 2 will be reversed under theinfluence of thermal disturbances or the like. For this reason, thecross-sectional area S of the magnetoresistance effect element 11 mustbe at least a predetermined size in order to ensure the stability ofmagnetic recording. In other words, in order to operate thespin-transfer torque type magnetoresistance effect element 101, acurrent amount obtained by multiplying the “current density necessaryfor magnetization reversal” with the “area for which magnetization canbe stably maintained” is necessary.

In contrast, in order to operate the spin-orbit torque typemagnetoresistance effect element 100 according to the presentembodiment, a current amount obtained by multiplying the “currentdensity necessary for magnetization reversal” with the “cross-sectionalarea of the spin-orbit torque wiring 20” is necessary. The“cross-sectional area of the spin-orbit torque wiring 20” can be set toany value. For this reason, in the spin-orbit torque typemagnetoresistance effect element 100, the total amount of currentnecessary for operation can be made smaller.

As illustrated in FIG. 1 , the second ferromagnetic metal layer 2 in thespin-orbit torque type magnetoresistance effect element 100 has shapeanisotropy. The length L1 of the second ferromagnetic metal layer 2 inthe x-direction is longer than the length (width) L2 in the y-direction.By configuring the spin-orbit torque type magnetoresistance effectelement 100 in this way, the total amount of current necessary foroperation can be made smaller. Herebelow, the reasons therefor will beexplained.

FIG. 4 is a schematic view of a spin-orbit torque type magnetoresistanceeffect element 102 when the second ferromagnetic metal layer 2 of themagnetoresistance effect element 12 does not have shape anisotropy. Inthe magnetoresistance effect element 12 illustrated in FIG. 4 , thelength L1′ of the second ferromagnetic metal layer 2 in the x-directionis equal to the length (width) L2′ in the y-direction. In other words,the magnetoresistance effect element 12 is square-shaped when viewedfrom the z-direction.

Generally speaking, when introducing elements of limited size into alimited space, elements having higher symmetry can be more efficientlyplaced. For this reason, in order to raise the level of integration ofMRAM, it would be normal to increase the symmetry of themagnetoresistance effect elements. In other words, magnetoresistanceeffect elements that are highly symmetrical, i.e. square-shaped (seeFIG. 4 ) or circular, when viewed from the z-direction, would be chosenfor use as the integrated elements.

In order to operate the spin-orbit torque type magnetoresistance effectelement 102, an electric current I₃ obtained by multiplying the “currentdensity I_(c3) necessary for magnetization reversal” with the“cross-sectional area (W′H) of the spin-orbit torque wiring 20” isnecessary. In other words, the relation I₃=I_(c3)×W′H is established.

As mentioned above, in order to operate the spin-orbit torque typemagnetoresistance effect element 100 illustrated in FIG. 1 , an electriccurrent I₁ obtained by multiplying the “current density I_(c1) necessaryfor magnetization reversal” with the “cross-sectional area (WH) of thespin-orbit torque wiring 20” is necessary. In other words, the relationI₁=I_(c1)×WH is established.

Since the layer structures of the magnctoresistance effect elements 10,12 are identical, the current density I_(c1) and the current densityI_(c3) are about the same. When considering that there is a need to makethe areas of magnetoresistance effect elements the same in order toensure thermal stability, the length L2′ of the magnetoresistance effectelement 12 in the y-direction must be made longer than the length L2,and in conjunction therewith, the width W′ of the spin-orbit torquewiring 20 in the y-direction must also be made wider. In other words,the width W′ of the spin-orbit torque type magnetoresistance effectelement 102 in the y-direction is wider than the width W of thespin-orbit torque type magnetoresistance effect element 100 in they-direction. In other words, the electric current I₁ that is necessaryto operate the spin-orbit torque type magnetoresistance effect element100 is lower than the electric current I₃ that is necessary to operatethe spin-orbit torque type magnetoresistance effect element 102.

In view of the above, it is preferable for the width W of themagnetoresistance effect element 10 to be as narrow as possible.However, when considering the state of the art in processing techniquessuch as photolithography, 7 nm is the limit. Additionally, the thicknessH of the spin-orbit torque wiring 20 is preferably as thin as possible,but the thickness should preferably be at least 10 nm in order to allowa sufficient amount of current to flow.

When the cross-sectional area of the spin-orbit torque wiring 20 issmall, the resistance can be expected to become greater. However, thespin-orbit torque wiring 20 is metallic and the resistance is notexpected to become so large that the operation of the element will beaffected. The increase in resistance is trivial in comparison to casesin which the electric current is supplied to a tunnel barrier layer, asin TMR elements in which magnetization reversal is performed by STT.

The resistance value at the portion of the spin-orbit torque wiring 20that overlaps with the magnetoresistance effect element 10 when viewedfrom the z-direction should preferably be lower than the resistancevalue of the magnetoresistance effect element 10. In this case, the“resistance value of the magnetoresistance effect element 10” refers tothe resistance value when electric current is supplied in thez-direction of the magnetoresistance effect element. Additionally, whenthe magnetoresistance effect element is a TMR, most of the resistance inthe magnetoresistance effect element 10 is due to the resistance in thetunnel barrier layer. By setting the resistance values to have such arelationship, it is possible to suppress the flow of the electriccurrent I₁ that is supplied to the spin-orbit torque wiring 20 into themagnetoresistance effect element 10. In other words, the electriccurrent I₁ supplied to the spin-orbit torque wiring 20 can be made tomore efficiently contribute to the generation of pure spin current.

Additionally, there is also the advantage that, when the secondferromagnetic metal layer 2 in the magnetoresistance effect element 10has shape anisotropy, the magnetization of the second ferromagneticmetal layer is more easily reversed. When the magnetization of thesecond ferromagnetic metal layer is oriented in the z-direction,magnetization rotation must be triggered in order to rotate themagnetization by SOT. The magnetization rotation may be triggered byapplying an external magnetic field or the like. However, if a magneticfield generation source is provided outside the element, the overallsize of the spin-orbit torque type magnetoresistance effect element 100will become large. Therefore, the magnetization rotation may betriggered, even in an environment lacking a magnetic field, by providingthe magnetoresistance effect element 10 with shape anisotropy.

When the second ferromagnetic metal layer 2 in the magnetoresistanceeffect element 10 has shape anisotropy, the intensity of thedemagnetizing field of the magnetoresistance effect element 10 willdiffer between the long-axis direction (direction of length L1) and theshort-axis direction (direction of length L2). In other words, therewill be a distribution in the intensity of the demagnetizing field.

The demagnetizing field is a reverse-oriented magnetic field that isgenerated inside a ferromagnetic body by the magnetic poles formed atthe ends of a magnetic body. For this reason, the intensity of thedemagnetizing field becomes greater as the polarizability of themagnetic poles becomes greater and as the distance between the magneticpoles becomes smaller. In the case of the magnetoresistance effectelement 10 illustrated in FIG. 1 , the intensity of the demagnetizingfield in the short-axis direction (direction of length L2) is greaterthan the intensity of the demagnetizing field in the long-axis direction(direction of length L1).

The demagnetizing field generates a restoring force that tends to returnthe magnetization of the second ferromagnetic metal layer to theoriginal state when the magnetization begins to rotate. The restoringforce counteracts the magnetization rotation, and as the restoring forcebecomes greater, it becomes more difficult to rotate the magnetization.

For this reason, the ease of rotation of the magnetization of the secondferromagnetic metal layer 2 differs between the rotation direction alongthe long-axis direction (hereinafter referred to as the first rotationdirection) and the rotation direction along the short-axis direction(hereinafter referred to as the second rotation direction). Theintensity of the restoring force that is encountered when rotating themagnetization is greater in the short-axis direction. For this reason,the magnetization is more easily rotated along the first rotationdirection than along the second rotation direction. In other words, thefirst rotation direction is a magnetization-reversal-facilitateddirection.

As illustrated in FIG. 3 , the magnetoresistance effect element 12,which is square-shaped in planar view when viewed from the z-direction,does not have a magnetization-reversal-facilitated direction.Additionally, when considering that it is necessary to make the areas ofmagnetoresistance effect elements the same in order to ensure thermalstability, the length L1 of the magnetoresistance effect element 10 inthe x-direction must be longer than the length L1′ of themagnetoresistance effect element 12 in the x-direction. In other words,the energy necessary for reversing the magnetization of themagnetoresistance effect element 10 is less than the energy necessaryfor reversing the magnetization of the magnetoresistance effect element12.

In this case, the length L1 of the magnetoresistance effect element 10in the long-axis direction should preferably be at least 10 nm and notmore than 60 nm, and the length L2 in the short-axis direction shouldpreferably be smaller than L1. When the size of the magnetoresistanceeffect element 10 is large, magnetic domains are formed inside thesecond ferromagnetic metal layer 2. When magnetic domains are formed,the stability of the magnetization of the second ferromagnetic metallayer decreases. Additionally, the length of the magnetoresistanceeffect element 10 in the long-axis direction is preferably at leasttwice, more preferably at least four times, the length in the short-axisdirection. If the ratio between the lengths of the magnetoresistanceeffect element 10 in the long-axis direction and the short-axisdirection is within said range, then a sufficient difference is obtainedin the restoring force due to the demagnetizing field.

FIG. 5 is a diagram illustrating the spin-orbit torque typemagnetoresistance effect element according to the present embodiment,when viewed from the z-direction. FIG. 5(a) corresponds to a diagramillustrating the spin-orbit torque type magnetoresistance effect element100 illustrated in FIG. 1 , when viewed from the z-direction. There areno particular limitations on the shape of the magnetoresistance effectelement as long as the length L1 in the x-direction is longer than thelength (width) L2 in the y-direction. The shape may be rectangular as inthe magnetoresistance effect element 10 illustrated in FIG. 5(a), orelliptical as in the magnetoresistance effect element 13 illustrated inFIG. 5(b).

As in the magnetoresistance effect element 14 illustrated in FIG. 5(c),the configuration may be such that the planar shape when viewed from thez-direction has an inscribed elliptical region E and external regions Aon the outside, in the x-direction, of the elliptical region E. Byretaining the external regions A, it is possible to make the area of themagnetoresistance effect element 14 larger. If the area of themagnetoresistance effect element 14 is made larger, the magnetizationstability is increased and magnetization reversals due to thermaldisturbances or the like can be avoided.

As in the magnetoresistance effect element 15 illustrated in FIG. 5(d),the long axis of the magnetoresistance effect element 10 may be inclinedby an angle θ with respect to the direction of extension (x-direction)of the spin-orbit torque wiring 20.

As mentioned above, the magnetization-reversal-facilitated direction isformed in the long-axis direction of the magnetoresistance effectelement 10. In other words, in the magnetoresistance effect element 15,the magnetization-reversal-facilitated direction has a component in they-direction.

The spin that is generated in the spin-orbit torque wiring 20 by thespin Hall effect is aligned with the outer surface of the spin-orbittorque wiring 20. In other words, the spin injected from the spin-orbittorque wiring 20 into the magnetoresistance effect element 10 isoriented in the y-axis direction. That is, the spin most efficientlycontributes to magnetization reversal of magnetization having acomponent in the y-direction.

In other words, due to the magnetization-reversal-facilitated directionof the magnetoresistance effect element 15 having a y-directioncomponent, the magnetization can be strongly influenced by SOT acting inthe y-direction. That is, the SOT can be made to efficiently act on themagnetization reversal, and the magnetization can be reversed withoutapplying any external forces such as an external magnetic field.

FIG. 6 is a diagram illustrating the spin-orbit torque typemagnetoresistance effect element according to the present embodiment,when viewed from the x-direction. FIG. 6(a) corresponds to a diagramillustrating the spin-orbit torque type magnetoresistance effect element100 illustrated in FIG. 1 when viewed from the x-direction. In FIG.6(a), the distance between the end portions of the spin-orbit torquewiring 20 and the magnetoresistance effect element 10 in the y-directionis the same at both sides. In other words, the following relationship isestablished.

The two end portions of the spin-orbit torque wiring 20 in they-direction are referred to as the first end portion e1 and the secondend portion e2. Additionally, the two end portions of themagnetoresistance effect element 10 in the y-direction are referred toas the third end portion e3 and the fourth end portion e4. The third endportion e3 is the end portion on the same side as the first end portione1, and the fourth end portion e4 is the end portion on the same side asthe second end portion e2. The distance D1 between the first end portione1 and the third end portion e3 is equal to the distance D2 between thesecond end portion e2 and the fourth end portion e4.

The distance D1 between the first end portion e1 and the third endportion e3 and the distance D2 between the second end portion e2 and thefourth end portion e4 are both greater than zero, and preferably, atleast one of the distances is not more than the spin diffusion length ofthe spin-orbit torque wiring 20.

When an electric current is supplied to the spin-orbit torque wiring 20,a pure spin current is generated between the first end portion e1 andthe third end portion e3 and between the second end portion e2 and thefourth end portion e4. The spin that is generated in these regions canpropagate within a distance range that is not more than the spindiffusion length. For this reason, if the distance D1 between the firstend portion e1 and the third end portion e3 and the distance D2 betweenthe second end portion e2 and the fourth end portion e4 are greater thanzero, then the spin generated in these regions can also be used formagnetization rotation. Additionally, if these distances are not morethan the spin diffusion length of the spin-orbit torque wiring 20, thenthe generated spin can all be used for magnetization reversal.

Additionally, FIG. 6(b) is a diagram illustrating another example of thespin-orbit torque type magnetoresistance effect element according to thepresent embodiment, when viewed from the x-direction. In FIG. 6(b), thedistance D1 between the first end portion e1 and the third end portione3 is greater than the distance D2 between the second end portion e2 andthe fourth end portion e4. In other words, the distance D1 between thefirst end portion e1 and the third end portion e3 is different from thedistance D2 between the second end portion e2 and the fourth end portione4.

The total amount of spin generated between the first end portion e1 andthe third end portion e3 is greater than the total amount of spingenerated between the second end portion e2 and the fourth end portione4. If the generated spin is all supplied to the magnetoresistanceeffect element 10, then the amount of spin supplied to the side of themagnetoresistance effect element 10 having the third end portion e3 willbe greater than the amount of spin supplied to the side having thefourth end portion e4. In other words, the symmetry in the intensity ofthe SOT in the y-direction for rotating the magnetization of themagnetoresistance effect element 10 will be disrupted.

As mentioned above, the spin that is injected from the spin-orbit torquewiring 20 into the magnetoresistance effect element 10 is oriented inthe y-axis direction. In other words, the spin most efficientlycontributes to magnetization reversal having a component in they-direction. For this reason, if the symmetry in the intensity of theSOT that is applied for the magnetization of the magnetoresistanceeffect element 10 in the y-direction is disrupted, then magnetizationreversal is made easier. As a result thereof, the SOT acts efficientlyfor magnetization reversal, and the magnetization can be reversed evenwithout applying an external force such as an external magnetic field.

With the spin-orbit torque type magnetoresistance effect elementaccording to the present embodiment, the total amount of the electriccurrent necessary for operation can be made smaller. For this reason,when integrated elements are connected to a power supply having apredetermined capacity, the electric current can be distributed to alarger number of elements.

Additionally, in the spin-orbit torque type magnetoresistance effectelement according to the present embodiment, there is no need to supplyelectric current in the stacking direction of the magnetoresistanceeffect element. Thus, the operating life of the magnetoresistance effectelement can be made longer.

Additionally, in the spin-orbit torque type magnetoresistance effectelement according to the present embodiment, a distribution in thedemagnetizing field occurs in conjunction with the shape anisotropy ofthe magnetoresistance effect element. As a result thereof, amagnetization-reversal-facilitated direction is formed in themagnetoresistance effect element, and the magnetization can be easilyreversed.

(Method for Producing Spin-Orbit Torque Type Magnetoresistance EffectElement)

Next, the method for producing the spin-orbit torque typemagnetoresistance effect element will be explained.

A spin-orbit torque type magnetoresistance effect element can beobtained by using a film deposition technique such as sputtering and ashape processing technique such as photolithography.

First, spin-orbit torque wiring is fabricated on a substrate forming asupport. The metal constituting the spin-orbit torque wiring isdeposited by a publicly known film deposition means such as sputtering.Next, a technique such as photolithography is used to process thespin-orbit torque wiring into a predetermined shape. Portions other thanthe spin-orbit torque wiring are covered by an insulating film such asan oxide film. The exposed surfaces of the spin-orbit torque wiring andthe insulating film should preferably be polished by means ofchemical-mechanical polishing (CMP).

Next, the magnetoresistance effect element is fabricated. Themagnetoresistance effect element can be fabricated using a publiclyknown film deposition means such as sputtering. If the magnetoresistanceeffect element is a TMR element, then a tunnel barrier layer can beformed, for example, by first sputtering approximately 0.4 to 2.0 nm ofmagnesium, aluminum and a metal thin-film that forms divalent cationswith multiple non-magnetic elements onto the second ferromagnetic metallayer, causing plasma oxidation or natural oxidation by feeding oxygen,and thereafter performing a heat treatment. The film deposition methodmay, aside from sputtering, be vapor deposition, laser ablation or MBE.

As the method for forming the magnetoresistance effect element into apredetermined shape, a processing means such as photolithography may beused. First, after forming the magnetoresistance effect element, aresist is applied to the surface of the magnetoresistance effect elementon the side opposite from the spin-orbit torque wiring. Next, the resistis cured at a predetermined portion and the unnecessary parts of theresist are removed. The cured portion of the resist forms a protectivefilm on the magnetoresistance effect element. The cured portion of theresist has the same shape as the magnetoresistance effect element thatis finally obtained.

Additionally, the surface on which the protective film is formed isprocessed by a technique such as ion milling or reactive ion etching(RIE). The portion on which the protective film is not formed isremoved, resulting in a magnetoresistance effect element of apredetermined shape.

The method for curing the resist in the predetermined shape will beexplained in detail.

As a first method, there is a method of sensitizing the resist to lightusing a mask. For example, a positive resist is used to form a photomaskon the portion that is to be cured. By exposing the resist to lightthrough the photomask, the resist can be processed to a predeterminedshape.

There is a demand for reducing the element size of magnetoresistanceeffect elements in order to allow higher integration. For this reason,the size of magnetoresistance effect elements may approach theresolution limit that is possible with light exposure. In this case, asillustrated in FIG. 7 , multiple photomasks PM that have been processedinto rectangular shapes are combined to cure the resist in thepredetermined shape. In the current state of the art, one side of onephotomask PM may be made as small as approximately a few nm.

FIG. 7 is a diagram illustrating the correspondence between the shape ofa photomask PM and the planar shape of the resulting magnetoresistanceeffect element 13, when viewed from the z-direction. As illustrated inFIG. 7(a), even when the shape of one photomask PM is rectangular, theplanar shape of the magnetoresistance effect element 13 becomeselliptical or the like. This is because some of the light that haspassed through the photomask PM is scattered and cures the resist.Additionally, in etching processes such as ion milling, etching proceedsmore easily in the areas forming corners.

When external regions A are to be formed outside an elliptical region Eas illustrated in FIG. 5(c), the photomask is shaped as shown in FIG.7(b) and FIG. 7(c). The photomask PM1 illustrated in FIG. 7(b) has arectangular region Re in which the ellipse can be inscribed, andprojecting regions Pr1 at the corners Ed of the rectangular region Re.Additionally, the photomask PM2 illustrated in FIG. 7(c) has arectangular region Re in which the ellipse can be inscribed, andprojecting regions Pr2 on the long sides Sd of the rectangular regionRe. The rectangular regions Re in FIGS. 7(b) and (c) correspond to thephotomask illustrated in FIG. 7(a).

By providing projecting regions Pr1 at the corners Ed as illustrated inFIG. 7(b), it is possible to delay the progress in the etching of thecorners Ed during the etching process. As a result thereof, externalregions A can be formed as illustrated in FIG. 5(c). Additionally, byproviding projecting regions Pr2 on the sides Sd as illustrated in FIG.7(c), the etching rate difference between the sides Sd and the cornersEd during the etching process can be made larger. As a result thereof,external regions A can be formed as shown in FIG. 5(c).

As another method, spot exposure can be performed by using light havingdirectionality, such as a laser. For example, a negative resist is used,and light is shone only at the portions that are to be cured, therebyprocessing the resist into a predetermined shape. In this case as well,even if the shape of the spot that is exposed is rectangular, theresulting shape will be elliptical.

As mentioned above, even if the shape of the photomask PM isrectangular, the shape of the magnetoresistance effect element 13 willbe a shape not having straight edges, such as an ellipse. For thisreason, modifications are needed if the planar shape of themagnetoresistance effect element 10 when viewed from the z-direction isto be made rectangular, as illustrated in FIG. 5(a).

When the planar shape of the magnetoresistance effect element 10 is tobe made rectangular when viewed from the z-direction, themagnetoresistance effect element 10 is processed in two steps. In otherwords, the process is divided into a first step of processing a stackedbody having the first ferromagnetic metal layer, and the non-magneticlayer and the second ferromagnetic metal layer in one direction, and asecond step of processing the stacked body, after having been processedin the one direction, in another direction that intersects with the onedirection.

FIG. 8 is a schematic view for explaining the procedure for fabricatinga rectangular magnetoresistance effect element. As illustrated in FIG.8(a), a second ferromagnetic metal layer 2, a non-magnetic layer 3 and afirst ferromagnetic metal layer 1 are sequentially stacked onto onesurface of spin-orbit torque wiring 20 and an insulator 50, resulting ina stacked body.

Next, the resulting stacked body is processed in one direction. Anydirection may be chosen as the one direction. For example, it may be thex-direction in which the spin-orbit torque wiring 20 extends, it may bethe y-direction orthogonal to the x-direction, or it may be a directionthat is oblique with respect to both the x-direction and they-direction.

The stacked body may be processed by using a publicly known processingmeans, such as a method using photolithography, or a method using alaser or the like. The stacked body, after processing, has some lengthin the one direction, and thus can directly reflect the shape of thephotomask or the like. In other words, the stacked body can be processedinto a straight line in the x-direction.

Next, the resulting stacked body is processed in another direction. Anydirection intersecting with the one direction may be chosen as the otherdirection. In FIG. 8(c), the stacked body is processed in they-direction that is orthogonal to the x-direction in which thespin-orbit torque wiring 20 extends.

The processing in the other direction may also be performed using apublicly known processing means, such as a method usingphotolithography, or a method using a laser or the like. It is alsopossible to use a photomask or the like having some length in the otherdirection when processing the stacked body in the other direction, sothe shape of the photomask or the like can thus be directly reflected inthe shape after processing. In other words, the stacked body can beprocessed into a straight line in the y-direction.

Thus, by processing the stacked body in two steps, it is possible tomake the planar shape of the magnetoresistance effect element 10rectangular when viewed from the z-direction.

Additionally, the outer surface of the resulting magnetoresistanceeffect element 10 may be covered by an insulator. The insulator may be apublicly known insulator such as an oxide film, a nitride film or thelike.

A method for fabricating the spin-orbit torque wiring and themagnetoresistance effect element sequentially has been explained to thispoint. On the other hand, it is also possible to fabricate thespin-orbit torque wiring and the magnetoresistance effect element at thesame time.

First, the metal layer constituting the spin-orbit torque wiring and thelayers constituting the magnetoresistance effect element aresequentially stacked onto a surface. Next, the spin-orbit torque wiringand the magnetoresistance effect element are processed together by meansof photolithography. In a single process, the processing of thespin-orbit torque wiring and the magnetoresistance effect element in afirst direction is completed simultaneously. Thereafter, by processingthe magnetoresistance effect element in a second direction differentfrom the first direction, a spin-orbit torque type magnetoresistanceeffect element is obtained.

The present invention is not necessarily limited to the structures andproduction methods of the spin-orbit torque type magnetoresistanceeffect element according to the above-described embodiments, and it ispossible to make various modifications within a range not departing fromthe spirit of the present invention.

(Integration Properties of Spin-Orbit Torque Type MagnetoresistanceEffect Element)

Next, the integration properties of the spin-orbit torque typemagnetoresistance effect element according to the present embodimentwill be explained.

<Circuit Structure>

FIG. 9 and FIG. 10 are diagrams schematically illustrating integratedcircuits in which a plurality of spin-orbit torque typemagnetoresistance effect elements 100 are integrated. The integratedcircuit 200 illustrated in FIG. 9 and the integrated circuit 201illustrated in FIG. 10 both have only slight current leakage duringwriting and reading, and the circuits function satisfactorily aselements. In the circuits in FIG. 9 and FIG. 10 , the spin-orbit torquewiring 20 is denoted as resistances 21 and 22.

In the integrated circuit 200 illustrated in FIG. 9 and the integratedcircuit 201 illustrated in FIG. 10 , a read control element 110, anelement selection control element 120 and a write control element 130are connected to one spin-orbit torque type magnetoresistance effectelement 100. As these control elements, publicly known transistors orthe like, such as FETs (field-effect transistors) are used.

When a read control element 110 and an element selection control element120 are activated (switched to the “ON” state), an electric current canbe supplied in the stacking direction of the magnetoresistance effectelement 10, and changes in the resistance value of the magnetoresistanceeffect element 10 can be read. Additionally, when a write controlelement 130 and an element selection control element 120 are activated(switched to the “ON” state), an electric current can be supplied to thespin-orbit torque wiring 20, and the magnetization of the secondferromagnetic metal layer 2 in the magnetoresistance effect element 10can be reversed (written).

In the integrated circuit 200 illustrated in FIG. 9 , the write controlelements 130 span across multiple spin-orbit torque typemagnetoresistance effect elements 100, and can be provided together onan end portion of the integrated circuit board or the like. In otherwords, in the integrated circuit 200 illustrated in FIG. 9 , the writecontrol elements 130 do not have much influence on the integrationproperties of the spin-orbit torque type magnetoresistance effectelement 100.

Similarly, in the integrated circuit 201 illustrated in FIG. 10 , theread control elements 110 span across multiple spin-orbit torque typemagnetoresistance effect elements 100, and can be provided together onan end portion of the integrated circuit board or the like. In otherwords, the read control elements 110 do not have much influence on theintegration properties of the spin-orbit torque type magnetoresistanceeffect element 100.

Therefore, a single unit cell that affects the integration properties ofthe integrated circuit can be considered to be formed by a singlespin-orbit torque type magnetoresistance effect element 100 and twocontrol elements. The two control elements are the read control element110 and the element selection control element 120 in the integratedcircuit 200 illustrated in FIG. 9 , and the element selection controlelement 120 and the write control element 130 in the integrated circuit201 illustrated in FIG. 10 .

Conventionally, it was thought that three control elements are necessaryfor each spin-orbit torque type magnetoresistance effect element 100using SOT. However, depending on the arrangement, it is possible toreduce the number of control elements affecting the integrationproperties to two.

<Consideration of Unit Cell Size>

Next, the size of a single unit cell will be considered. A single unitcell is defined by one spin-orbit torque type magnetoresistance effectelement 100 and two control elements. For this reason, the manner inwhich these elements are to be arranged is an important problem.Additionally, it is necessary to estimate the element sizes that arenecessary for appropriately operating the spin-orbit torque typemagnetoresistance effect element 100 and the two control elements.

Additionally, the respective element sizes necessary for appropriatelyoperating the spin-orbit torque type magnetoresistance effect element100 and the two control elements will be estimated.

(Spin-Orbit Torque Type Magnetoresistance Effect Element Size)

In SRAM (Static Random Access Memory) using spin-transfer torque(Hereinafter referred to as “STT-SRAM”), as one example, cylindricalmagnetoresistance effect elements having a diameter of 90 nm are used.In this case, the cross-sectional area of a magnetoresistance effectelement when viewed from the stacking direction is (90/2)²×π=6361 nm².Magnetoresistance effect elements having cross-sectional areas of thissize can stably retain data for 10 years even when subjected toinfluences such as thermal disturbances.

The cross-sectional area of a magnetoresistance effect element that isnecessary for stably retaining data is also about the same for thespin-orbit torque type magnetoresistance effect element 100 according tothe present embodiment. For this reason, when a magnetoresistance effectelement is viewed from the stacking direction, a cross-sectional area ofapproximately 6300 nm² is necessary. This cross-sectional areacorresponds to the value of the “length L1 in the x-direction”multiplied by the “length L2 in the y-direction” in FIG. 1 .

The length L1 in the x-direction and the length L2 in the y-directioncan be set to any value. Currently, the smallest processing size(feature size: F) that is possible in a semiconductor is considered tobe 7 nm. For this reason, the length L2 in the y-direction must be, atminimum, 7 nm, in which case the length in the x-direction would be 900nm. Other values could also be set for the length L1 in the x-directionand the length L2 in the y-direction, as shown in Table 1 below. In allcases, “length L2 in the y-direction”×“length L1 in thex-direction”≈6300 nm², and data can be stably retained.

On the other hand, in order to allow use as a memory element, the datamust be capable of being rewritten.

In order to reverse the magnetization of (rewrite the data in) amagnetoresistance effect element in STT-SRAM, a current amount obtainedby multiplying the “cross-sectional area of the magnetoresistance effectelement” with the “current density necessary for magnetization reversal”is necessary. For example, if the current amount is 400 CIA, then thecurrent density that is necessary for magnetization reversal is 400μA/6361 nm²=6.2×10⁶ A/cm².

In order to rewrite the data in the spin-orbit torque typemagnetoresistance effect element 100 according to the presentembodiment, an electric current value obtained by multiplying the“current density necessary for magnetization reversal” with the“cross-sectional area (WH) of the spin-orbit torque wiring 20” isnecessary.

Since the cross-sectional areas of the magnetoresistance effect elementsare the same, the “current density necessary for magnetization reversal”will not significantly differ from the current density that is necessaryfor magnetization reversal of the magnetoresistance effect elements inSTT-SRAM. In other words, it may be 6.2×10⁶ A/cm².

The “cross-sectional area (WH) of the spin-orbit torque wiring 20” isdetermined as follows. The width W of the spin-orbit torque wiring 20must be at least the length L2 of the magnetoresistance effect element10 in the y-direction. The thickness H of the spin-orbit torque wiring20 must be approximately 10 nm in order to supply enough electriccurrent, although this depends also on the width W of the spin-orbittorque wiring 20.

In other words, the minimum electric current that is necessary torewrite the data in the spin-orbit torque type magnetoresistance effectelement 100 according to the present embodiment is a value obtained bymultiplying the “length L2 in the y-direction (=width W of thespin-orbit torque wiring 20)” and the “thickness H of the spin-orbittorque wiring 20” with the “current density necessary for magnetizationreversal”.

Table 1 shows the current amounts that are necessary in themagnetoresistance effect element 10 for different lengths L1 in thex-direction and lengths L2 in the y-direction. All of the currentamounts are values that are well short of the 400 μA that are necessaryfor magnetization reversal in STT-SRAM having the same level of dataretention performance.

TABLE 1 Spin-Orbit Torque Type Magnetoresistance Effect ElementMagnetoresistance Effect Element Control Element By By Spin-Orbit TorqueWiring By Width L2 Minimum Width L1 Minimum Cross- Minimum Integrated inProcessing in Processing sectional Reversal FET Processing Circuity-direction Size x-direction Size Width Thickness Area Current WidthSize Cell Area (nm) (n₂F) (nm) (n₁F) (nm) (nm) (nm²) (μA) (nm) (n₃F)(F²) Example 1 7 1F 900 129F  7 10 70 4.3 8.68 2F 1056 Example 2 14 2F450 65F 14 10 140 8.7 17.36 3F 544 Example 3 21 3F 300 43F 21 10 21013.0 26.04 4F 368 Example 4 28 4F 225 33F 28 10 280 17.4 34.72 5F 288Example 5 35 5F 180 26F 35 10 350 21.7 43.4 7F 232 Example 6 42 6F 15022F 42 10 420 26.0 52.08 8F 200 Example 7 49 7F 129 19F 49 10 490 30.460.76 9F 176 Example 8 56 8F 113 17F 56 10 560 34.7 69.44 10F  160Example 9 63 9F 100 15F 63 10 630 39.1 78.12 12F  144 Example 10 70 10F 90 13F 70 10 700 43.4 86.8 13F  128 Example 11 77 11F  82 12F 77 10 77047.7 95.48 14F  136Size of Control Elements

On the other hand, the electric current necessary for magnetizationreversal is controlled by means of the respective control elements. Inother words, each control element must have the ability to supply theelectric current necessary for magnetization reversal. In other words,the element size necessary for each control element can be estimatedfrom the current amount necessary for magnetization reversal.

FIG. 11 is a schematic perspective view illustrating a main portion of acontrol element used in the spin-orbit torque type magnetoresistanceeffect element according to the present embodiment. Since the sameelement may be used for the read control element 110, the elementselection control element 120 and the write control element 130, theelement shall be explained herebelow as the control element T. Asillustrated in FIG. 11 , the control element T comprises a sourceelectrode S, a drain electrode D and a channel C.

If the width of the source electrode S, the width of the drain electrodeD and the distance between the source electrode S and the drainelectrode D are fixed at the minimum processing size F, then apredetermined current amount per unit width Wa that can be suppliedbetween the source electrode S and the drain electrode D can bedetermined. When the unit width is 1 μm, an example of the predeterminedcurrent amount would be 0.5 mA. In this case, if the reversal currentthat is necessary for magnetization reversal is 4 μA as in Example 1shown in Table 1, then the width Wc of the control element must be atleast 8 μm. Table 1 also shows the widths Wc of the control element thatare necessary in other examples.

As mentioned above, it is possible to estimate the respective elementsizes that are necessary for appropriately operating a spin-orbit torquetype magnetoresistance effect element 100 and two control elements T.Next, the manner in which one spin-orbit torque type magnetoresistanceeffect element 100 and two control elements T are to be arranged will beconsidered.

Element Arrangement: First Arrangement

FIG. 12 is a diagram for explaining the cell size necessary forarranging one spin-orbit torque type magnetoresistance effect elementand two control elements.

Expressing the size of the spin-orbit torque type magnetoresistanceeffect element 100 in terms of the minimum processing size, the lengthL1 in the x-direction is n₁F and the length L2 in the y-direction isn₂F. Although n₁ and n₂ are designable values, they are correlated asshown in Table 1.

On one hand, the length of one side of a control element T must be 3F inorder to be able to accommodate the width of the source electrode, thewidth of the drain electrode and the channel region between the sourceelectrode and the drain electrode. On the other hand, the length n₃F ofthe other side is determined by the current amount to be supplied to thechannel C (see Table 1).

These elements are disposed inside a predetermined region R. Thespin-orbit torque type magnetoresistance effect element 100 and thecontrol elements T do not need to be processed so as to be on the sameplane, and they may overlap when viewed from the z-direction. Incontrast, the control elements T are arranged in parallel in they-direction in order to route the wiring or the like.

FIG. 13 is a schematic perspective view illustrating the elementstructure of a unit cell when one spin-orbit torque typemagnetoresistance effect element and two control elements are arrangedin accordance with the arrangement in FIG. 12 . In FIG. 13 , an elementselection control element 120 and a write control element 130 areincorporated as the control elements in a unit cell, and the structureis in accordance with the circuit diagram in FIG. 10 . As illustrated inFIG. 13 , the wiring that connects the three control elements is routedwithout resulting in any short circuits. In other words, it can be seenthat the arrangement of the control elements illustrated in FIG. 12 isalso possible when taking the three-dimensional structure into account.It was also confirmed that a three-dimensional structure is possiblewhen following the circuit diagram in FIG. 9 (not shown in perspective).

As illustrated in FIG. 12 and FIG. 13 , a space is needed betweenadjacent elements that are present on the same plane in order to avoidshort circuits between the elements. This space must have a gap of atleast the minimum processing size F. In other words, a width of at least8F is necessary in the y-direction for a unit cell in the integratedcircuit.

In the x-direction of the unit cell in the integrated circuit, the sizemust be at least as large as either the length (n₁F) of the spin-orbittorque type magnetoresistance effect element 100 in the x-direction orthe length (n₃F) of the control element T in the x-direction. In actualpractice, a space (2F) for fabricating a through-via B (see FIG. 12 )and a space (1F) for separating adjacent elements are required, so thewidth must be at least 3F added to either the length (n₁F) of thespin-orbit torque type magnetoresistance effect element 100 in thex-direction or the length (n₃F) of the control element T in thex-direction, whichever is greater.

In this case, it is assumed that the size of the through-via B need onlybe the minimum processing size F in one direction. However, in actualpractice, the size that is needed for fabricating a through-via B willdiffer depending on the manufacturer used. For this reason, if the sizethat is necessary for fabricating the through-via B is different, thenit is necessary to add a value of twice said size in the x-direction.The reason the value must be doubled is because two through-vias arenecessary. Additionally, in the y-direction, if a through-via B cannotbe overlapped with a control element when viewed from the z-direction,then the size thereof also must be added to 8F.

Although the addition of through-via sizes affects the absolute value ofthe cell area, the relative relationships are not affected. For thisreason, even if calculations are made using hypothetical numericalvalues, the relative sizes will not change.

As shown in Table 1, in most cases apart from Example 11, the length(n₁F) of the spin-orbit torque type magnetoresistance effect element 100in the x-direction determines the size necessary in the x-direction fora unit cell in an integrated circuit.

As mentioned above, the cell area necessary for a unit cell in theintegrated circuit is 8F×{(n₁F or n₃F)+3}. In this case, the larger of“n₁F or n₃F” is chosen. The cell areas that are necessary for differentshapes of the magnetoresistance effect element are shown in Table 1.

The cell area becomes larger as the difference between the width L1(n₁F) of the magnetoresistance effect element 10 in the x-direction andthe width (n₃F) of the control element T in the x-direction becomesgreater. This is because, as illustrated in FIG. 12 , the dead space DSin which no elements are formed increases. In other words, for thepurposes of integration, it is preferable for the difference between thewidth L1 (n₁F) of the magnetoresistance effect element 10 in thex-direction and the width (n₃F) of the control element T in thex-direction to be smaller. As illustrated in FIG. 14 , the level ofintegration can be increased by arranging the spin-orbit torque typemagnetoresistance effect element 100 and the control elements T so as tofill in the dead space DS.

Meanwhile, in order to make the reversal current amount smaller, it ispreferable to make the width L2 (n₂F) of the magnetoresistance effectelement 10 in the y-direction smaller, even if the difference betweenthe width L (n₂F) of the magnetoresistance effect element 10 in thex-direction and the width (n₃F) of the control element T in thex-direction becomes greater.

Additionally, the results of a similar analysis when assuming theminimum processing size F to be 10 nm are shown in Table 2, and theresults of a similar analysis when assuming the minimum processing sizeF to be 28 nm are shown in Table 3. Similar results were able to beconfirmed in Tables 2 and 3.

TABLE 2 Spin-Orbit Torque Type Magnetoresistance Effect ElementMagnetoresistance Effect Element Control Element By By Spin-Orbit TorqueWiring By Width L2 Minimum Width L1 Minimum Cross- Minimum Integrated inProcessing in Processing sectional Reversal FET Processing Circuity-direction Size x-direction Size Width Thickness Area Current WidthSize Cell Area (nm) (n₂F) (nm) (n₁F) (nm) (nm) (nm²) (μA) (nm) (n₃F)(F²) Example 12 10 1F 630 63F 10 10 100 6.2 12.4 2F 528 Example 13 20 2F315 32F 20 10 200 12.4 24.8 3F 280 Example 14 30 3F 210 21F 30 10 30018.6 37.2 4F 192 Example 15 40 4F 158 16F 40 10 400 24.8 49.6 5F 152Example 16 50 5F 126 13F 50 10 500 31 62 7F 128 Example 17 60 6F 105 11F60 10 600 37.2 74.4 8F 112 Example 18 70 7F 90  9F 70 10 700 43.4 86.89F 96

TABLE 3 Spin-Orbit Torque Type Magnetoresistance Effect ElementMagnetoresistance Effect Element Control Element By By Spin-Orbit TorqueWiring By Width L2 Minimum Width L1 Minimum Cross- Minimum Integrated inProcessing in Processing sectional Reversal FET Processing Circuity-direction Size x-direction Size Width Thickness Area Current WidthSize Cell Area (nm) (n₂F) (nm) (n₁F) (nm) (nm) (nm²) (μA) (nm) (n₃F)(F²) Example 19 28 1F 225 9F 28 10 280 17.4 34.7 2F 80 Example 20 56 2F113 4F 56 10 560 34.7 69.4 3F 40 Comparative 84 3F 75 3F 84 10 840 52104.16 4F 56 Example 1 Comparative 112 4F 56 3F 112 10 1120 69 138.88 5F64 Example 2 Comparative 140 5F 45 2F 140 10 1140 87 173.6 7F 80 Example3 Comparative 168 6F 38 2F 168 10 1680 104 208.32 8F 88 Example 4Comparative 196 7F 32 2F 196 10 1960 122 243.04 9F 96 Example 5

In Comparative Examples 1-5, the width L2 of the magnetoresistanceeffect element in the y-direction is greater than the width L1 in thex-direction, and a large reversal current amount is necessary formagnetization reversal. Additionally, the width of the cell area of theintegrated circuit in the x-direction is dependent on the size of thecontrol elements and the level of integration is made worse.

Element Arrangement: Second Arrangement

In the above-described first arrangement, the control elements arearranged in parallel in the y-direction, but the control elements T mayalso be arranged in parallel in the x-direction.

FIG. 15 is a diagram for explaining the cell size necessary forarranging one spin-orbit torque type magnetoresistance effect elementand two control elements. FIG. 16 is a schematic perspective viewillustrating the element structure of a unit cell when one spin-orbittorque type magnetoresistance effect element and two control elementsare arranged in accordance with the arrangement in FIG. 15 .

In FIG. 16 , an element selection control element 120 and a writecontrol element 130 are incorporated as the control elements in a unitcell, and the structure is in accordance with the circuit diagram inFIG. 10 . As illustrated in FIG. 16 , the wiring that connects the threecontrol elements is routed without resulting in any short circuits. Inother words, it can be seen that the arrangement of the control elementsillustrated in FIG. 16 is also possible when taking thethree-dimensional structure into account. It was also confirmed that athree-dimensional structure is possible when following the circuitdiagram in FIG. 9 (not shown in perspective).

As illustrated in FIG. 15 , the sizes of the elements are not different.However, by changing the arrangement, the width in the x-direction thatis necessary for providing two control elements changes. The width inthe x-direction that is necessary for two control elements is twice thewidth (3F) of each element in the x-direction, plus the distance (n₄F)between the elements. Since the minimum distance between the elements isF, the width in the x-direction that is necessary for the two controlelements must be, at minimum, 7F. Additionally, 1F is necessary in orderto ensure separation between adjacent unit cells, so at least 8F isnecessary.

In other words, when the value (n₁F+2F+F) obtained by adding space (2F)for through-vias and space (F) between the cells to the length of thespin-orbit torque type magnetoresistance effect element 100 in thex-direction is greater than the minimum length (8F) of the controlelements T in the x-direction, the size of the former (n₁F+2F+F) isnecessary in the x-direction for a unit cell in the integrated circuit.Meanwhile, if the value (n₁F+2F) obtained by adding the space for twothrough-vias to the length of the spin-orbit torque typemagnetoresistance effect element 100 in the x-direction is smaller thanthe minimum length (8F) of the control elements T in the x-direction,the size of the latter (8F) is necessary in the x-direction for a unitcell in the integrated circuit.

On the other hand, in the y-direction of a unit cell in the integratedcircuit, the size must be at least either the length (n₂F) of thespin-orbit torque type magnetoresistance effect element 100 in they-direction or the length (n₃F) of a control element T in they-direction. In actual practice, a space (1F) for separating adjacentelements is required, so the width must be at least F added to eitherthe length (n₂F) of the spin-orbit torque type magnetoresistance effectelement 100 in the y-direction or the length (n₃F) of a control elementT in the y-direction, whichever is greater.

For this reason, the cell area necessary for a unit cell in theintegrated circuit is {(n₁F+2F+F) or 8F}×{(n₂F+F) or (n₃F+F)}. The “or”in the cell area measurement calculation indicates that the larger ofthe two values is chosen.

The cell areas that are necessary for different shapes of themagnetoresistance effect element, when the minimum processing size F isassumed to be 7 nm, are shown in Table 4. The cell areas that arenecessary for different shapes of the magnetoresistance effect element,when the minimum processing size F is assumed to be 10 nm, are shown inTable 5. The cell areas that are necessary for different shapes of themagnetoresistance effect element, when the minimum processing size F isassumed to be 28 nm, are shown in Table 6. Since the sizes of theelements are unchanged, the values other than the cell sizes of theintegrated circuits match with those in Tables 1 to 3.

TABLE 4 Spin-Orbit Torque Type Magnetoresistance Effect ElementMagnetoresistance Effect Element Control Element By By Spin-Orbit TorqueWiring By Width L2 Minimum Width L1 Minimum Cross- Minimum Integrated inProcessing in Processing sectional Reversal FET Processing Circuity-direction Size x-direction Size Width Thickness Area Current WidthSize Cell Area (nm) (n₂F) (nm) (n₁F) (nm) (nm) (nm²) (μA) (nm) (n₃F)(F²) Example 21 7 1F 900 129F  7 10 70 4.3 8.68 2F 396 Example 22 14 2F450 65F 14 10 140 8.7 17.36 3F 272 Example 23 21 3F 300 43F 21 10 21013.0 26.04 4F 230 Example 24 28 4F 225 33F 28 10 280 17.4 34.72 5F 216Example 25 35 5F 180 26F 35 10 350 21.7 43.4 7F 232 Example 26 42 6F 15022F 42 10 420 26.0 52.08 8F 225 Example 27 49 7F 129 19F 49 10 490 30.460.76 9F 220 Example 28 56 8F 113 17F 56 10 560 34.7 69.44 10F  220Example 29 63 9F 100 15F 63 10 630 39.1 78.12 12F  234 Example 30 7010F  90 13F 70 10 700 43.4 86.8 13F  224 Example 31 77 11F  82 12F 77 10770 47.7 95.48 14F  225

TABLE 5 Spin-Orbit Torque Type Magnetoresistance Effect ElementMagnetoresistance Effect Element Control Element By By Spin-Orbit TorqueWiring By Width L2 Minimum Width L1 Minimum Cross- Minimum Integrated inProcessing in Processing sectional Reversal FET Processing Circuity-direction Size x-direction Size Width Thickness Area Current WidthSize Cell Area (nm) (n₂F) (nm) (n₁F) (nm) (nm) (nm²) (μA) (nm) (n₃F)(F²) Example 32 10 1F 630 63F 10 10 100 6.2 12.4 2F 198 Example 33 20 2F315 32F 20 10 200 12.4 24.8 3F 140 Example 34 30 3F 210 21F 30 10 30018.6 37.2 4F 120 Example 35 40 4F 158 16F 40 10 400 24.8 49.6 5F 114Example 36 50 5F 126 13F 50 10 500 31 62 7F 128 Example 37 60 6F 105 11F60 10 600 37.2 74.4 8F 126 Example 38 70 7F 90  9F 70 10 700 43.4 86.89F 120

TABLE 6 Spin-Orbit Torque Type Magnetoresistance Effect ElementMagnetoresistance Effect Element Control Element By By Spin-Orbit TorqueWiring By Width L2 Minimum Width L1 Minimum Cross- Minimum Integrated inProcessing in Processing sectional Reversal FET Processing Circuity-direction Size x-direction Size Width Thickness Area Current WidthSize Cell Area (nm) (n₂F) (nm) (n₁F) (nm) (nm) (nm²) (μA) (nm) (n₃F)(F²) Example 39 28 1F 225 9F 28 10 280 17.4 34.7 2F 36 Example 40 56 2F113 4F 56 10 560 34.7 69.4 3F 32 Comparative 84 3F 75 3F 84 10 840 52104.16 4F 40 Example 6 Comparative 112 4F 56 3F 112 10 1120 69 138.88 5F48 Example 7 Comparative 140 5F 45 2F 140 10 1140 87 173.6 7F 64 Example8 Comparative 168 6F 38 2F 168 10 1680 104 208.32 8F 72 Example 9Comparative 196 7F 32 2F 196 10 1960 122 243.04 9F 80 Example 10

REFERENCE SIGNS LIST

-   1 First ferromagnetic metal layer-   2 Second ferromagnetic metal layer-   3 Non-magnetic layer-   10, 11, 12, 13, 14, 15 Magnetoresistance effect element-   20 Spin-orbit torque wiring-   30 First wiring-   40 Second wiring-   50 Insulator-   100, 102 Spin-orbit torque type magnetoresistance effect element-   101 Spin-transfer torque type magnetoresistance effect element-   110 Read control element-   120 Element selection control element-   130 Write control element-   T Control element-   S Source electrode-   D Drain electrode-   C Channel-   e1 First end portion-   e2 Second end portion-   e3 Third end portion-   e4 Fourth end portion-   S1 First spin-   S2 Second spin-   I Electric current-   Js Pure spin current-   PM Photomask

What is claimed is:
 1. A magnetization rotational element, comprising: aferromagnetic metal layer with a varying magnetization direction; and aspin-orbit torque wiring that extends in a first direction intersectingwith a plane-orthogonal direction of the ferromagnetic metal layer andthat the ferromagnetic metal layer being located on one surface of thespin-orbit torque wiring, wherein the magnetization of the ferromagneticmetal layer is oriented in the plane-orthogonal direction of theferromagnetic metal layer; a planar shape of the magnetizationrotational element when viewed from the plane-orthogonal direction ofthe ferromagnetic metal layer has an elliptical region that is inscribedin the planar shape of the magnetization rotational element, and anexternal region that is positioned outside the elliptical region in thefirst direction.
 2. A magnetization rotational element, comprising: aferromagnetic metal layer with a varying magnetization direction; and aspin-orbit torque wiring that extends in a first direction intersectingwith a plane-orthogonal direction of the ferromagnetic metal layer andthat the ferromagnetic metal layer being located on one surface of thespin-orbit torque wiring, wherein the magnetization of the ferromagneticmetal layer is oriented in the plane-orthogonal direction of theferromagnetic metal layer; a length of the magnetization rotationalelement in the first direction is not more than 60 nm.
 3. Amagnetization rotational element, comprising: a ferromagnetic metallayer with a varying magnetization direction; and a spin-orbit torquewiring that extends in a first direction intersecting with aplane-orthogonal direction of the ferromagnetic metal layer and that theferromagnetic metal layer being located on one surface of the spin-orbittorque wiring, wherein the magnetization of the ferromagnetic metallayer is oriented in the plane-orthogonal direction of the ferromagneticmetal layer; when end portions of the spin-orbit torque wiring in thesecond direction are defined as a first end portion and a second endportion; and end portions of the magnetization rotational element in thesecond direction are defined as a third end portion and a fourth endportion, wherein the third end portion is closer to the first endportion and the fourth end portion is closer to the second end portion,and a distance between the first end portion and the third end portionand a distance between the second end portion and the fourth end portionare both greater than zero, and at least one of the distances is notmore than a spin diffusion length of a material used for forming thespin-orbit torque wiring.
 4. The magnetization rotational elementaccording to claim 3, wherein the distance between the first end portionand the third end portion is different from the distance between thesecond end portion and the fourth end portion.
 5. A method for producinga magnetization rotational element the method comprising: a step offorming the ferromagnetic metal layer; a step of forming, on one surfaceof the ferromagnetic metal layer, a mask having a rectangular region inwhich an ellipse can be inscribed when viewed from the stackingdirection of the ferromagnetic metal layer, and a projecting region thatis positioned at a corner or a long side of the rectangular region andthat projects from the rectangular region; and a step of processing theferromagnetic metal layer through the mask; wherein the magnetizationrotational element, comprises: a ferromagnetic metal layer with avarying magnetization direction; and a spin-orbit torque wiring thatextends in a first direction intersecting with a plane-orthogonaldirection of the ferromagnetic metal layer and that the ferromagneticmetal layer being located on one surface of the spin-orbit torquewiring, wherein the magnetization of the ferromagnetic metal layer isoriented in the plane-orthogonal direction of the ferromagnetic metallayer.
 6. A magnetization rotational element, comprising: aferromagnetic metal layer with a varying magnetization direction; and aspin-orbit torque wiring that extends in a first direction intersectingwith a plane-orthogonal direction of the ferromagnetic metal layer andthat the ferromagnetic metal layer being located on one surface of thespin-orbit torque wiring, wherein the magnetization of the ferromagneticmetal layer is oriented in the plane-orthogonal direction of theferromagnetic metal layer; when viewed from the plane-orthogonaldirection of the ferromagnetic metal layer, when end portions of thespin-orbit torque wiring in the second direction are defined as a firstend portion and a second end portion; and end portions of theferromagnetic metal layer in the second direction are defined as a thirdend portion and a fourth end portion, wherein the third end portion iscloser to the first end portion and the fourth end portion is closer tothe second end portion, and a distance between the first end portion andthe third end portion and a distance between the second end portion andthe fourth end portion are both greater than zero.
 7. The magnetizationrotational element according to claim 6, wherein a long axis of themagnetization rotational element is inclined by an angle θ with respectto the first direction.
 8. A magnetization rotational element,comprising: a ferromagnetic metal layer with a varying magnetizationdirection; and a spin-orbit torque wiring that extends in a firstdirection intersecting with a plane-orthogonal direction of theferromagnetic metal layer and that the ferromagnetic metal layer beinglocated on one surface of the spin-orbit torque wiring, wherein themagnetization of the ferromagnetic metal layer is oriented in theplane-orthogonal direction of the ferromagnetic metal layer, a firstlength (L1) of the magnetization rotational element in the firstdirection is 82 nm or more and 900 nm or less, a second length (L2) ofthe magnetization rotational element in the second direction is 7 nm ormore and 77 nm or less, and a product of the first length and the secondlength (L1×L2) is 6300 nm² or more.